The present invention relates to a compression-bond-connection substrate to be connected to other members by pressure-bonding. The invention also relates to a liquid crystal device comprised of the compression-bond-connection substrate. Also, the invention relates to an electronic equipment comprised of the liquid crystal device.
Currently, liquid crystal devices are being widely used in various types of electronic devices, such as portable telephones and portable information terminals. In most of these devices, liquid crystal devices are used to display visual information including characters, numbers, and graphical patterns.
The liquid crystal devices are generally comprised of substrates opposing each other and a liquid crystal sealed between the substrates. In the liquid crystal devices, there is a case in which a compression-bond-connection substrate is connected to either one or both of the substrates. The compression-bond-connection substrate has a drive circuit for driving the liquid crystal device. In the drive circuit, elements including IC chips and passive-element chip parts are mounted, and wiring patterns required to connect the abovementioned elements are formed. Also, substrate-side terminals are formed to conductively connect to terminals on the side of the liquid crystal device at appropriate locations on the compression-bond-connection substrate.
Compression-bonding processing conductively connects substrate-side terminals formed on the compression-bond-connection substrate to terminals formed on the substrates of the liquid crystal device (that is, opposing-side terminals). The compression-bonding processing uses an anisotropic conductive adhesive, such as an ACF (anisotropic conductive film), an ACP (anisotropic conductive paste), or an ACA (anisotropic conductive adhesive). The processing is performed in such a manner that the anisotropic conductive adhesive is sandwiched between the substrate of the liquid crystal device and the compression-bond-connection substrate, and the adhesive is then heated and pressed by using a compression-bonding tool.
As compression-bond-connection substrates, a single-sided wired type, a double-sided wired type, and a multilayer wired type can be considered. The single-sided wired type is a wiring type in which all elements, such as the drive circuit, wiring patterns, and substrate-side terminals are formed on a single side of the substrate. The double-sided wired type is a wiring type in which elements such as the drive circuit, wiring patterns, and substrate-side terminals are separated so as to be arranged on both sides of the substrate, and they become conductive through conductive throughholes as required. The multilayer wired type is a wiring type in which a wiring layer is repeatedly layered with an insulating layer therebetween, and individual layers become conductive through conductive throughholes as required.
FIG. 8 shows a state in which an ACF 51 is used to connect a compression-bond-connection substrate 53 of the double-sided wired type to a compression-bonding target object 52 by compression-bonding. In the state shown, a compression-bonding tool 55 heats the ACF 51 arranged between the compression-bonding target object 52 and the compression-bond-connection substrate 53 at a predetermined temperature and concurrently presses it with a pressure F. The ACF 51 is then caused to harden, resulting in compression-bonding of the compression-bonding target object 52 and the compression-bond-connection substrate 53. By compression-bonding, a plurality of lands 54 formed on the compression-bond-connection substrate 53 are individually conductively connected to bumps 56 of the compression-bonding target object 52 via conductive balls 59 in the ACF 51.
In the case of the aforementioned conventional compression-bond-connection substrate 53 of the double-sided wired type, however, while the lands 54 as substrate-side terminals are formed on the compression-bonding side surface, backside wiring patterns 58 are formed on the reverse side of the compression-bonding-side surface. Therefore, the plurality of lands 54 includes both types of lands 54a overlapping with the backside wiring patterns 58 and lands 54b not overlapping with the backside wiring patterns 58.
In the case of the compression-bond-connection substrate 53 as described above, when compression-bonding is carried out by using the compression-bonding tool 55, a high pressure is exerted on the lands 54a overlapping with the backside wiring patterns 58 whereas an insufficient pressure is exerted on the lands 54b not overlapping with the backside wiring patterns 58. This causes the connection between the plurality of bumps 56 and the plurality of lands 54 to be partially insufficient, significantly reducing the reliability of the connection therebetween.
A connection assembly as shown in FIG. 8 uses the compression-bond-connection substrate 53 of the double-sided wired type having a configuration in which the wiring layers are formed on both the front side and the backside of the substrate. Nevertheless, a problem similar to the above arises even in a compression-bond-connection substrate of the multilayer wired type having a configuration in which multiple wiring layers are overlaid.
The present invention is to provide a compression-bond-connection substrate such as that of a double-sided wired type or multilayer wired type that has a configuration in which multiple wiring layers are overlaid, which allows stable provision of a highly reliable compression-bonding connected assembly.
The present invention provides a compression-bond-connection substrate to be connected by compression-bonding to a compression-bonding target object having opposing-side terminals, comprising a compression-bonding-side surface to be connected to the compression-bonding target object, substrate-side terminals formed on the compression-bonding side surface to be conductively connected to the opposing-side terminals, and backside wiring patterns formed on the reverse face of the compression-bonding-side surface, characterized in that step compensation patterns having substantially the same thickness as that of the backside wiring patterns are formed on the reverse face in positions corresponding to the backsides of the substrate-side terminals.
In the present invention as described above, as shown in FIG. 5 for example, when a compression-bond-connection substrate 3 is compression-bonded with a compression-bonding target object 2, an adhesive material 1 such as an ACF is sandwiched therebetween; and furthermore, the adhesive material 1 is heated, and concurrently, both the compression-bonding target object 2 and the compression-bond-connection substrate 3 are pressed together with a pressure F. At this time, substrate-side terminals 4 formed on a compression-bonding-side surface of the compression-bond-connection substrate 3 are conductively connected to opposing-side terminals 6 formed on the compression-bonding target object 2.
According to the present invention, step compensation patterns 7 having the same thickness as that of backside wiring patterns 8 are formed in positions at the backsides of the substrate-side terminals 4 where the backside wiring patterns do not exist on a reverse face of the compression-bonding side surface of the compression-bond-connection substrate 3. Therefore, the pressure is applied uniformly by a compression-bonding tool 5 to the individual substrate-side terminals 4. As a result, all the individual substrate-side terminals 4 can be ensured to be conductively connected to,all the individual opposing-side terminals 6. That is, according to the compression-bond-connection substrate of the present invention, even in the case of a substrate on which a plurality of wiring patterns overlap with each other, as in a double-sided wired type or a multilayer wired type, a highly reliable compression-bonded assembly can be obtained.
Also, in the compression-bond-connection substrate having the above configuration, at least some of the step compensation patterns may be formed on the reverse face of the compression-bonding side surface in positions corresponding to the backsides of regions overlapping with a plurality of the substrate-side terminals. Even in this case, effects similar to the above case can be obtained.
Also, in the compression-bond-connection substrate having the above configuration, the compression-bonding target object may be, for example, an IC chip, and in this case, the opposing-side terminals may be considered as bumps to be formed on an active face of the IC chip.
Also, in the compression-bond-connection substrate having the above configuration, the compression-bonding target object may be, for example, a substrate of a liquid crystal panel including a pair of substrates opposing each other and a liquid crystal sealed between the substrates.
Also, in this case, the opposing-side terminals may be considered as external-connecting terminals formed on at least either one of the pair of substrates of a liquid crystal panel.
Also, the compression-bond-connection substrate having the above configuration is characterized so as to be conductively connected to the compression-bonding target object via an anisotropic conductive adhesive.
In the present invention as described above, as shown in FIG. 5 for example, the anisotropic conductive adhesive as an adhesive material 1 is sandwiched, and furthermore, the anisotropic conductive adhesive is heated, and concurrently, a compression-bonding target object 2 and the compression-bond-connection substrate 3 are pressed together with a pressure F. At this time, the substrate-side terminals 4 formed on the compression-bonding-side surface of the compression-bond-connection substrate 3 are conductively connected to the opposing-side terminals 6 formed on the compression-bonding target object 2. As a result, a highly reliable compression-bonded assembly can be obtained.
Also, the present invention provides a liquid crystal device comprising a pair of substrates opposing each other, a liquid crystal enclosed between the substrates, and a compression-bond-connection substrate connected at least to one of the pair of substrates, characterized in that the compression-bond-connection substrate is composed as described above.
According to the liquid crystal device, even in the case that a compression-bond-connection substrate connected to the liquid crystal side substrate is a substrate on which a plurality of wiring patterns overlap with each other, as in a double-sided wired type or a multilayer wired type, a highly reliable compression-bonded assembly can be obtained. Therefore, occurrence of display defects due to failed electrical conductivity can be avoided.
Also, the present invention provides an electronic equipment comprised of a liquid crystal device, characterized in that the liquid crystal device is as described above, allowing provision of an electronic equipment in which effects similar to the above can be obtained. As electronic devices of this type, devices such as portable telephones and portable information terminals can be considered.